Tactical voting

[jack]

I think I'm sufficiently decided about the euro elections, but I had some left over thoughts.

D'Hondt method

Have I understood this right?

Suppose there's 7 seats available for a number of parties. Then every party whose vote share exceeds 1/7 of the votes, is guaranteed at least as many seats as they have whole sevenths of the vote share? That'd accord with what I'd do so far.

But if I were running it, then I'd say, give the remaining seats to the parties who are closest to one more seat than they already have (whether that's 6 seats but nearly 7 seats, or no seats but nearly 1 seat). But D'Hondt counts your remainder more, in proportion to how many seats you already have?

Why on earth is it like that? Is it supposed to avoid niche parties? Or is it just that it's longstanding and superficially reasonable, so when the voting method was chosen they chose the most FPTP like proportional system they could get away with?

East of England

There were several helpful "tactical voting guides" going around, but several seemed to concentrate more than I'd originally realised on "trust our subjective judgements without asking too many questions" rather than on providing data.

My natural choice would be Lib Dem or Green, mostly as a clear "Remain" vote. Which I prefer depends on circumstance, but I was also trying to figure out if it would make a difference if I wanted to increase the chance of either winning a seat.

Previously Lib Dem have held about 15% of the vote and I think got an MEP, although last euro elections they were at a lower point. The greens have previously been lower, but have been creeping up over time, especially if people are finally starting to pay SOME attention to mitigating climate change.

So it sounds like I'm right, if lib dem are around 15% and greens are lower it would be worth voting lib dem to make sure to push them up over the 1/7 boundary? But if lib dem were already higher than that and green were approaching it, it would be better to vote green to get *them* closer to a seat (unless lib dem were doing so well they were close to 30%).

But that's sufficiently precise it's almost pointless to try to predict, so I should go for whichever I prefer, or whichever I think has the highest support?

Comments

[naath]

If party A had 1000 votes, party B 900 votes and part c 300 votes.

A wins, and gets MEP 1; their vote is now 1000/2=500
B now wins, gets MEP 2; their vote is now 900/2=450
A wins, gets MEP 3; now 1000/3=333 1/3
B wins, gets MEP 4; now 900/3=300
A get MEP 5; now 1000/4=250
B get MEP 6; now 900/4=225
C get MEP 7 since 300 is > 250 and 225.

D'Hondt is annoying. I don't know what you meant by 'closest to one more'.

If A had 100 and B had 600 (so A has 1/7th) B's total is 600 (win 1), 300 (win 2), 200 (win 3), 150 (win 4), 120 (win 5), 100 (er, tied for 6 & 7, I don't know what the tie-break is but either way one each).

If 7 parties each had approximately 1/7th the vote they would each get 1 MEP and then be sent to less than anyone else's votecount.

So yes I think 1/7th guarantees you an MEP, but you clearly don't need 1/7th if the vote is very split. It is known to favour large parties, and the list system favours internal party folks who are likely to be part of/pay attention to list-deciding systems.

[jack]

I don't know what you meant by 'closest to one more'.

I'm struggling for a clear example. Say, there's 100 voters. Bigparty has 91% of the vote. Smallparty has 9% of the vote. Bigparty clearly has 9 seats. But that last 10% is a lot lot more towards Smallparty than towards Bigparty. Bigparty would need another 9% of the vote to get another seat. Smallparty would need only 1% more.

But in D'Hondt, Bigparty's share is 91/(9+1) = 9.1% so they get the last seat as well. (Have I got that maths right?) I'd heard "biased towards", but that seems like a really big distortion.

[naath]

After taking the 6th seat Big has 91/7=13 which remains larger than 9 and takes the seat. Small would need another 4 seats to tie or 5 to unambiguously take the seat, 50% more votes than they got, I'm not seeing that as 'close' even if as a small party voter I would often like to see small party get an oar in at the big table.

6/7 of 100 is about 85; and yes 91-85=6 and 6<9; this might make a good system although I'm not sure it has had all the edges filed off, but it is not D'Hondt which is definately bigparty-favouring, and a long way from my favourite voting system.

[jack]

Doh, sorry! I was working an example for 10 seats in the hope that would make the numbers simpler, but somehow I actually left that out of the premise :(

[naath]

10 seats 91v9 votes then 9 seats go to Big and now Big has 91/(9+1)=9.1 which is... just bigger than 9; see big party favouring system. If you did 10% = 1 MEP and subtract 10 percentage points from total ending with parties get 1 seat each in order of largest amount left until full Big would get 9 seats leaving 91-(10*9)=1 vote, and 1 is < 9 so Small takes the last.

D'Hondt is not mandated by the EU; indeed NI does a preference voting based system (I don't know which) and they are even in the UK; we chose this rubbish system ourselves.

[jack]

see big party favouring system

Right, I just hadn't realised how MUCH it did. I guess it's better than FPTP but it seems a real shame we ended up with this.

[naath]

Not much better, which is probably how we got it

[andrewducker]

There are two kinds of ways of dealing with proportional systems - Highest Average (like D'hondt) and Largest Remainder (Hamilton).

Largest Remainder (which I think you're advocating) is good in some ways, but can suffer the Alabama Paradox, where adding a seat means that some of the parties get _less_ seats.

See https://en.wikipedia.org/wiki/Largest_remainder_method for a good breakdown of the good and bad sides.

[jack]

Ah, I see! Thank you. OK, that is a sensible reason to use d'Hondt (although I might still pick something else anyway)

[andrewducker]

Be interested to see what conclusion you come to.

(Some would go a completely different way and pick STV as a voting method, which is great in some ways, but has its own issues)

[jack]

About which voting system to use or which party to vote for?

I'm not sure I know enough to pick a *right* voting system. If I had the choice I think I would prefer something more like highest remainder, but I'm not certain. I would definitely choose something more STV-ish than the current system if I could, but I don't know exactly what. I guess it would be worth having a single right answer people in favour of reform could all push behind, but it feels like a mess having to choose when most things would be an improvement over the status quo (although the voting reform referendum showed how that goes wrong).

I decided with all of the pros and cons, both in terms of how much I liked them and tactically, green beat out lib dem just slightly, but I wasn't very sure. I think it probably didn't make that much difference. I forgot TIG/CUK were standing, but I don't think that would have been any better.